Non-volatile memory device with vertical memory cells and method for fabricating the same

ABSTRACT

A non-volatile memory device includes a plurality of gate electrodes stacked over a semiconductor substrate and stretched in a first direction along the semiconductor substrate and a plurality of junction layers having a first region protruding from the semiconductor substrate and crossing the gate electrodes and a second region formed between the gate electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority of Korean Patent Application No.10-2011-0084122, filed on Aug. 23, 2011, which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field

Exemplary embodiments of the present invention relate to a semiconductordevice and a fabrication method thereof, and more particularly, to anon-volatile memory device and a fabrication method thereof.

2. Description of the Related Art

When a single layer of memory cells are formed over a monocrystallinesilicon substrate, a memory density thereof is determined based onpatterning limitation and packaging limitation. The packaging limitationmay be relaxed by decreasing the size of patterns so as to increase thememory density.

However, as patterning technology reaches the technical limitation, itis difficult to further increase the memory density. In suchcircumstances that there are increased demands for the increase in thememory density, forming a single layer of memory cells over amonocrystalline silicon substrate may not satisfy the demands. Here, thememory density signifies the number of memory cells formed in a unitarea.

SUMMARY

An embodiment of the present invention is directed to a non-volatilememory device that may include more memory cells than a conventionalnon-volatile memory device regardless of the area of a substrate, and amethod for fabricating the non-volatile memory device.

In accordance with an embodiment of the present invention, anon-volatile memory device includes: a plurality of gate electrodesstacked over a semiconductor substrate and stretched in a firstdirection along the semiconductor substrate; and a plurality of junctionlayers having a first region protruding from the semiconductor substrateand crossing the gate electrodes and a second region formed between thegate electrodes.

In accordance with another embodiment of the present invention, anon-volatile memory device includes: a plurality of cell channel layersand a plurality of gate electrodes that are alternately stacked over asemiconductor substrate and stretched in a first direction along thesemiconductor substrate; and a plurality of junction layers protrudingfrom the semiconductor substrate, crossing the gate electrodes, andcoupled with the cell channel layers.

In accordance with yet another embodiment of the present invention, amethod for fabricating a non-volatile memory device includes: forming astack layer by alternately stacking a first conductive layer, a firstinsulation layer, and a second insulation layer over a semiconductorsubstrate; forming first openings and a plurality of gate electrodesthat are isolated from each other by the first openings by etching thestack layer; forming a third insulation layer filling the firstopenings; forming second openings by selectively etching the thirdinsulation layer; forming third openings by removing the secondinsulation layer that is exposed on sidewalls of the second openings;forming a charge trapping dielectric layer over the semiconductorsubstrate having the third openings formed therein; and forming ajunction layer and a cell channel layer over the charge trappingdielectric layer to fill the second openings and the third openings,respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an equivalent circuit diagram of a non-volatile memory devicein accordance with a first embodiment of the present invention.

FIG. 2 is a projection view of the non-volatile memory device inaccordance with the first embodiment of the present invention.

FIGS. 3A to 3J are cross-sectional views illustrating a method forfabricating a non-volatile memory device taken along a line A-A′ of FIG.2.

FIGS. 4A to 4H are cross-sectional views illustrating a method forfabricating a non-volatile memory device taken along a line B-B′ of FIG.2.

FIG. 5A is a plan view illustrating a structure including junctionlayers and cell channel layers in accordance with the first embodimentof the present invention.

FIG. 5B is a plan view illustrating a modified example of the structureincluding junction layers and cell channel layers in accordance with thefirst embodiment of the present invention.

FIGS. 6 and 7 are perspective views illustrating a non-volatile memorydevice in accordance with the first embodiment of the present invention.

FIGS. 8A to 8E are cross-sectional views illustrating a method forfabricating a non-volatile memory device in accordance with a secondembodiment of the present invention.

FIG. 9 is a plan view illustrating a structure including junction layersand cell channel layers in accordance with the second embodiment of thepresent invention.

FIGS. 10 and 11 are perspective views illustrating a non-volatile memorydevice in accordance with the second embodiment of the presentinvention.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the present invention tothose skilled in the art. Throughout the disclosure, like referencenumerals refer to like parts throughout the various figures andembodiments of the present invention.

The drawings are not necessarily to scale and in some instances,proportions may have been exaggerated in order to clearly illustratefeatures of the embodiments. When a first layer is referred to as being“on” a second layer or “on” a substrate, it not only refers to a casewhere the first layer is formed directly on the second layer or thesubstrate but also a case where a third layer exists between the firstlayer and the second layer or the substrate.

According to an embodiment of the present invention, memory cells areformed in a multi-layer structure by stacking memory cells in adirection perpendicular to a silicon substrate.

The following embodiment provides a flash memory device, in particular,an ORNAND-type flash memory device. The ORNAND-type flash memory devicemay also be referred to as NROM.

FIG. 1 is an equivalent circuit diagram of a non-volatile memory devicein accordance with a first embodiment of the present invention. To bespecific, FIG. 1 shows an ORNAND-type flash memory device.

Referring to FIG. 1, each memory cell is coupled with a word line thatfunctions as a control gate in a memory cell array, and a pair of memorycells shares a common bit line A0 or A1. For example, the memory cellarray in the embodiment is coupled with a selection transistor (Tr).

Depending on how memory cells are coupled with bit lines in response toa word line voltage, the memory cells may write, read, and erase bits ofdata. Reading a first bit of the data, for example, ‘A’ bit of a memorycell, is carried out by applying the word line voltage and coupling adrain and a source of the memory cell with a bit line A1 and a bit lineA0, respectively. Similarly, reading a second bit of the data, forexample, ‘B’ bit of a memory cell, is carried out by coupling a drainwith a bit line A0 and coupling a source with a bit line A1. Themulti-bits of the data may be stored by a charge trapping dielectriclayer disposed between a bit line and a word line. The charge trappingdielectric layer includes multiple dielectric layers, for example, oxidelayers, and a charge trapping layer, for example, a nitride layer,interposed between the multiple dielectric layers. Since the chargetrapping dielectric layer has the stacked structure, the charge trappingdielectric layer is referred to as an ONO (oxide-nitride-oxide) layer.

FIG. 2 is a projection view of the non-volatile memory device inaccordance with the first embodiment of the present invention.

Referring to FIG. 2, the non-volatile memory device includes a pluralityof gate electrodes that are stretched in a first direction and stackedin a vertical direction from a substrate, junction layers 111A stretchedin a second direction crossing the gate electrodes, i.e., protruding inthe vertical direction from the substrate, and cell channel layers 111Bformed between the stacked gate electrodes. The gate electrodes arestacked vertically over a semiconductor substrate and the plane-shapedcell channel layers 111B are disposed between the gate electrodes. Sincethe cell channel layers 111B and the gate electrodes are overlapped, thereference numeral of the gate electrodes is omitted. The junction layers111A have a shape of pillars stretched vertically from the semiconductorsubstrate and coupled with the cell channel layer 111B. Here, areference numeral ‘105’ indicates pillars formed between the stackedgate electrodes. The pillars 105 are of a nitride material. One pillar105 may be formed for one cell channel layer 111B. A selection gate 113of a selection transistor is formed in a direction crossing the junctionlayers 111A and the gate electrodes.

FIGS. 3A to 3J are cross-sectional views illustrating a method forfabricating a non-volatile memory device taken along a line A-A′ of FIG.2. FIGS. 4A to 4H are cross-sectional views illustrating a method forfabricating a non-volatile memory device taken along a line B-B′ of FIG.2.

Referring to FIGS. 3A and 4A, a buffer layer 102 are formed over asemiconductor substrate 101. The semiconductor substrate 101 includes amonocrystalline silicon substrate. The buffer layer 102 may be an oxidelayer, such as a silicon oxide layer.

A stack layer is formed over the buffer layer 102. The stack layer isformed by stacking a plurality of insulation layers and a plurality ofconductive layers. For example, the stack layer is formed by stackingfirst conductive layers 103A, 103B, 103C and 103D, first insulationlayers 104A, 104B, 104C and 104D, and second insulation layers 105A,105B and 105C. The first insulation layers 104A, 104B, 104C and 104Dinclude an oxide layer, such as a silicon oxide layer. The secondinsulation layers 105A, 105B and 105C include a nitride layer, such as asilicon nitride layer. The first conductive layers 103A, 103B, 103C and103D include a polysilicon layer. When the stack layer is formed bystacking the first conductive layers 103A, 103B, 103C and 103D, thefirst insulation layers 104A, 104B, 104C and 104D, and the secondinsulation layers 105A, 1053 and 105C, the lowermost layer may be madeby the first conductive layer 103A and the uppermost layer may be madeby the first insulation layer 104D.

The first conductive layers 103A, 103B, 103C and 103D function as gateelectrodes. In other words, the first conductive layers 103A, 103B, 103Cand 103D become control gate electrodes or word lines. The firstconductive layers 103A, 103B, 103C and 103D may include metal other thanpolysilicon or both polysilicon and a metal oxide. Also, the firstconductive layers 103A, 103B, 103C and 103D may include a metalcompound, such as a metal silicide, e.g., CoSix and NiSix. When thefirst conductive layers 103A, 103B, 103C and 103D are formed ofpolysilicon, a metal compound, e.g., CoSix and NiSix, may be furtherincluded by forming an opening region through the subsequent process toreduce resistance.

According to an embodiment of the present invention, the firstconductive layers 103A, 103B, 103C and 103D, the first insulation layers104A, 104B, 104C and 104D, and the second insulation layers 105A, 105Band 105C are stacked over the substrate 101 by being disposedalternately. For example, a first conductive layer, a first insulationlayer, and a second insulation layer are alternately stacked in thementioned order in multiple times, while the first insulation layer 104Dis disposed as the uppermost layer. In the drawing, the first conductivelayers 103A, 103B, 103C and 103D and the first insulation layers 104A,104B, 104C and 104D are stacked in four times, while the secondinsulation layers 105A, 105B and 105C are stacked in three times. Sincethe first conductive layers 103A, 103B, 103C and 103D, the firstinsulation layers 104A, 104B, 104C and 104D, and the second insulationlayers 105A, 105B and 105C are polysilicon layers, oxide layers, andnitride layers, respectively, the stack layer has a stacked structure ofpolysilicon/oxide/nitride/polysilicon/oxide/nitride/polysilicon/oxide/nitride/polysilicon/oxide.The number of stacking the first conductive layers 103A, 103B, 103C and103D is the same as the number of memory cells stacked in a line. Inshort, when the first conductive layers 103A, 103B, 103C and 103D arestacked in four times, the number of memory cells formed in the verticaldirection becomes four.

Referring to FIG. 3B and 4B, first openings 106 are formed byselectively etching the stack layer. The first openings 106 are thespace for isolating gate electrodes and they have a shape of trench. Inshort, the first conductive layers become gate electrodes 103A, 103B,103C and 103D by the first openings 106. The gate electrodes 103A, 103B,103C and 103D have a shape of lines stretched in a first direction. Thefour gate electrodes 103A, 103B, 103C and 103D are stacked in thevertical direction by being insulated from each other by the firstinsulation layers 104A, 104B, 104C and 104D and the second insulationlayers 105A, 105B and 105C. The gate electrodes 103A, 103B, 103C and103D may be also referred to as control gate electrodes or word lines.

Referring to FIGS. 3C and 4C, a third insulation layer 107 is formed togap-fill the first openings 106. The third insulation layer 107insulates neighboring gate electrodes of the same level of the stacklayer from each other. The third insulation layer 107 may be formed ofan oxide, such as a silicon oxide. The third insulation layer 107 isplanarized to expose the upper surface of the stack layer.

Referring to FIGS. 3D and 4D, second openings 108 are formed byselectively etching the third insulation layer 107. The second openings108 are the space for a source region and a drain region.

In a plan view, the second openings 108 may have a shape of circularholes or polygonal holes, and the diameter of each opening is formed tobe less than approximately 1 μm. Hereafter, the second openings 108 isillustrated to have a rectangular shape according to an example.

A photoresist pattern may be formed as an etch barrier for 1D formingthe second openings 108. For example, a photoresist pattern is formed tohave a shape of lines stretched in a second direction crossing the firstdirection of the gate electrodes 103A, 103B, 103C and 103D. Theremaining third insulation layer excluding the second openings 108 isreferred to as a third insulation layer pattern 107A, hereafter.

Referring to FIGS. 3E and 4E, the second insulation layers 105A, 105Band 105C exposed on the sidewalls of the second openings 108 areselectively removed. Since the second insulation layers 105A, 105B and105C are nitride layers, they may be selectively removed through a wetetch process using phosphoric acid (H₃PO₄) without damage to the firstinsulation layers 104A, 104B, 104C and 104D and the gate electrodes103A, 103B, 103C and 103D.

Since the second insulation layers 105A, 105B and 105C are removed,third openings 109 are formed between the gate electrodes 103A, 103B,103C and 103D and the first insulation layers 104A, 104B, 104C and 104D.The third openings 109 are referred to as an undercut. As a result, thethird openings 109 are formed between the multiple gate electrodes 103A,103B, 103C and 103D that are stacked in the vertical direction.

When the third openings 109 are formed, a photoresist pattern may beformed to prevent the multiple gate electrodes 103A, 103B, 103C and 103Dfrom collapsing. For example, the line-type photoresist layer patternthat has been used during the formation of the second openings 108 isused or a photoresist layer pattern having a wider linewidth is used.With the photoresist layer pattern, a portion of each second insulationlayer remains to function as a supporter (refer to a reference numeral‘105’ of FIG. 4E) that supports the gate electrodes.

Referring to FIGS. 3F and 4F, a charge trapping dielectric layer 110 isformed over the substrate structure including the second openings 108.The charge trapping dielectric layer 110 includes a gate insulationlayer, a charge trapping layer, and a tunnel insulation layer. In short,the gate insulation layer, the charge trapping layer, and the tunnelinsulation layer are sequentially stacked. The tunnel insulation layermay have a thickness of approximately 1 Å to approximately 200 Å. Theupper insulation layer may have a thickness of approximately 1 Å toapproximately 500 Å. The charge trapping layer may be a nitride layer.The charge trapping layer may have a thickness of approximately 1 Å toapproximately 500 Å. The upper insulation layer may be formed of asilicon oxide. The upper insulation layer may be formed of a materialhaving a greater dielectric constant than the silicon oxide. Metalmaterial may be injected into the charge trapping layer asimpurity/specks.

Referring to FIGS. 3G and 4G, a second conductive layer 111 filling thesecond openings 108 and the third openings 109 is formed over the chargetrapping dielectric layer 110. The second conductive layer 111 may beformed to have a predetermined thickness over the uppermost layer of thestack layer. The second conductive layer 111 is a material that is usedas channels and source/drains of a memory cell.

The second conductive layer 111 may be polysilicon layer. The secondconductive layer 111 may be formed of a conductive layer, other thansilicon. Also, the second conductive layer 111 may be formed bydenaturing a non-conductive material into a conductive material byimplanting an impurity into the non-conductive material. Also, thesecond conductive layer 111 may be formed of metal.

According to a first fabrication method, the second conductive layer 111is formed of an undoped polysilicon.

Referring to FIGS. 3H and 4H, the second conductive layer 111 isselectively etched. As a result, the second conductive layer remaininginside the second openings becomes junction layers 111A, and the secondconductive layer remaining inside the third openings between the gateelectrodes becomes a cell channel layer 111B. The upper portion of thesecond conductive layer remains as the form of pillars, and thepillar-shaped upper portion becomes the channels 111C of selectiontransistors.

FIG. 5A is a plan view illustrating a structure including junctionlayers and cell channel layers in accordance with the first embodimentof the present invention. Here, the junction layers 111A and the cellchannel layers 1118 are coupled with each other. The cell channel layers111B are penetrated by pillars, i.e., the second insulation layer 105,and the third insulation layer pattern 107A remains between the junctionlayers 111A. For the purpose of the description, the charge trappingdielectric layer 110 around the second insulation layer 105 and thethird insulation layer pattern 107A is omitted from the FIG. 5A.

FIG. 5B is a plan view illustrating a modified example of the structureincluding junction layers and cell channel layers in accordance with thefirst embodiment of the present invention. Here, the junction layers111A and the cell channel layers 1118 are coupled with each other. Thecell channel layers 111B formed on the lines where the second insulationlayer 105 and the third insulation layer pattern 107A are formed (i.e.,in the B-B′ direction) are removed.

Referring to FIG. 3I, selection transistors are formed to select astring of memory cells having a vertical structure. Each selectiontransistor includes a selection gate 113 and a gate insulation layer112. In other words, the gate insulation layer 112 surrounding thechannels 111C is formed, and then the selection gates 113 are formed. Athird insulation layer 114 for inter-layer insulation is formed overeach selection gate 113.

Referring to FIG. 33, bit lines 115 for applying a current and a voltageare formed over the channels 111A.

Meanwhile, the selection transistors and the bit lines are not formed inthe B-B′ direction.

FIGS. 6 and 7 are perspective views illustrating a non-volatile memorydevice in accordance with the first embodiment of the present invention.FIG. 6 shows a resultant substrate structure after the junction layers111A and the cell channel layers 111B are formed, and FIG. 7 shows aresultant substrate structure after the selection transistors areformed.

Referring to FIGS. 6 and 7, the buffer layer 102 is formed over thesemiconductor substrate 101, and the junction layers 111A having a shapeof pillars stretched in the vertical direction are formed over thebuffer layer 102. The cell channel layers 111B and the gate electrodes103A, 103B, 103C and 103D are alternately stacked in multiple times. Thecharge trapping dielectric layer 110 is formed between the gateelectrodes 103A, 103B, 103C and 103D and the cell channel layers 111B.The charge trapping dielectric layer 110 surrounds the gate electrodes103A, 103B, 103C and 103D. The cell channel layers 111B and the junctionlayers 111A are integrated with each other. The channels 111C of theselection transistors are formed in the upper portions of the junctionlayers 111A. The gate electrodes 103A, 103B, 103C and 103D have a shapeof plane stretched in the first direction, and the junction layers 111Ahave a shape of pillars stretched in the second direction crossing thegate electrodes 103A, 103B, 103C and 103D, i.e., in the verticaldirection. The selection gates 113 of the selection transistors arestretched in a third direction crossing the junction layers 111A and thegate electrodes 103A, 103B, 103C and 103D.

FIGS. 8A to 8E are cross-sectional views illustrating a method forfabricating a non-volatile memory device in accordance with a secondembodiment of the present invention. The processes until the chargetrapping dielectric layer is formed are the same as the first embodimentof the present invention.

Referring to FIG. 8A, a charge trapping dielectric layer 110 is formedthrough the process illustrated in FIGS. 3A to 3F.

Subsequently, a second conductive layer 201 is formed over the chargetrapping dielectric layer 110 to fill second openings and thirdopenings. The second conductive layer 201 may be formed to have apredetermined thickness over the uppermost layer of the stack layer. Thesecond conductive layer 201 is used as cell channels of a memory cell.

The second conductive layer 201 may be a polysilicon layer. For example,the second conductive layer 201 may be a polysilicon layer doped with anN-type impurity or a P-type impurity.

Referring to FIG. 8B, the second conductive layer inside the secondopenings is selectively removed. As a result, a second conductive layerpattern 201A remains inside the third openings, and the second openings108 are formed again. Hereafter, the second conductive layer pattern201A becomes cell channel layers 201A.

Referring to FIG. 8C, a third conductive layer 202 is formed to fill thesecond openings 108. The third conductive layer 202 may be a polysiliconlayer. According to an embodiment of the present invention, the thirdconductive layer 202 may be a polysilicon layer doped with an impurity.When the cell channel layers 201A are polysilicon layers each doped witha P-type impurity, the third conductive layer 202 is formed to be apolysilicon layer doped with an N-type impurity. In short, the cellchannel layers 201A and the third conductive layer 202 are formed to bethe polysilicon layers but doped with impurities of opposite conductivetypes.

Referring to FIG. 8D, the third conductive layer 202 is selectivelyetched. As a result, junction layers 202A remaining inside the secondopenings is formed. The upper portion of the third conductive layerremains as the shape of pillars, which become the channels 202B of theselection transistors.

The junction layers 202A and the cell channel layers 201A are coupledwith each other.

FIG. 9 is a plan view illustrating a structure including the junctionlayers 202A and the cell channel layers 201A in accordance with thesecond embodiment of the present invention. The junction layers 202A andthe cell channel layers 201A are coupled with each other. The cellchannel layers 201A are penetrated by pillars, i.e., the secondinsulation layer 105, and a third insulation layer pattern 107A remainsbetween the junction layers 202A.

Subsequently, selection transistors are formed to select a string ofmemory cells having a vertical structure. Each selection transistorincludes a selection gate 204 and a gate insulation layer 203. In otherwords, the gate insulation layer 203 surrounding the channels 202B isformed, and then the selection gates 204 are formed. A third insulationlayer 205 for inter-layer insulation is formed over each selection gate204.

Referring to FIG. 8E, bit lines 206 for applying a current and a voltageare formed over the junction layers 202A.

FIGS. 10 and 11 are perspective views illustrating a non-volatile memorydevice in accordance with the second embodiment of the presentinvention. FIG. 10 shows a resultant substrate structure after thejunction layers 202A and the cell channel layers 201A are formed, andFIG. 11 shows a resultant substrate structure after the selectiontransistors are formed.

Referring to FIGS. 10 and 11, the buffer layer 102 is formed over thesemiconductor substrate 101, and the junction layers 202A having a shapeof pillars stretched in the vertical direction are formed over thebuffer layer 102. The cell channel layers 201A and the gate electrodes103A, 103B, 103C and 103D are alternately stacked in multiple times. Acharge trapping dielectric layer 110 is formed between the gateelectrodes 103A, 103B, 103C and 103D and the cell channel layers 201A.The charge trapping dielectric layer 110 surrounds the gate electrodes103A, 103B, 103C and 103D. The cell channel layers 201A and the junctionlayers 202A are integrated with each other. The channels 202B of theselection transistors are formed in the upper portions of the junctionlayers 202A. The gate electrodes 103A, 103B, 103C and 103D have a shapeof plane stretched in the first direction, and the junction layers 202Ahave a shape of pillars stretched in the second direction crossing thegate electrodes 103A, 1036, 103C and 103D, i.e., in the verticaldirection. The selection gates 204 of the selection transistors arestretched in a third direction crossing the junction layers 202A and thegate electrodes 103A, 103B, 103C and 103D.

According to the above described embodiments of the present invention,the density of memory cells formed in a unit area of a semiconductorsubstrate may be increased more than two times. The increase in thememory density is obtained by controlling the number of the firstinsulation layers and the second insulation layers that are stacked.Also, since the gate electrodes are coupled with the channels except thespace for the deposition of a gate material, resistance becomes low andthe time delay caused by the gate loading effect may be minimized.

According to another embodiment of the present invention, as an unitdevice formed over a semiconductor substrate, NOR cells may be formed ina vertical structure, instead of a structure where memory cells areformed as a single layer, and also vertical memory cells of a DynamicRandom Access Memory (DRAM) device may be formed in the same method.

According to an embodiment of the present invention, the memory densitymay be substantially increased regardless of the area of a siliconsubstrate and patterning limitation.

In addition, since memory integration rate may be increased byincreasing the number of the memory gates, the production cost may begreatly decreased.

While the present invention has been described with respect to thespecific embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1-12. (canceled)
 13. A method for fabricating a non-volatile memorydevice, comprising: forming a stack layer by alternately stacking afirst conductive layer, a first insulation layer, and a secondinsulation layer over a semiconductor substrate; forming first openingsand a plurality of gate electrodes that are isolated from each other bythe first openings by etching the stack layer; forming a thirdinsulation layer filling the first openings; forming second openings byselectively etching the third insulation layer; forming third openingsby removing the second insulation layer that is exposed on sidewalls ofthe second openings; forming a charge trapping dielectric layer over thesemiconductor substrate having the third openings formed therein; andforming a junction layer and a cell channel layer over the chargetrapping dielectric layer to fill the second openings and the thirdopenings, respectively.
 14. The method of claim 13, further comprising:forming a channel layer by selectively etching an upper portion of thejunction layer; forming a selection gate of a selection transistorsurrounding the channel layer; and forming a bit line coupled with thechannel layer.
 15. The method of claim 13, wherein the charge trappingdielectric layer is formed by stacking a gate insulation layer, a chargetrapping layer, and a tunnel insulation layer.
 16. The method of claim13, wherein the second openings are formed as holes of circular orpolygonal shapes.
 17. The method of claim 13, the forming of thejunction layer and the cell channel layer comprises: forming a secondconductive layer filling the second openings and the third openings overthe charge trapping dielectric layer; forming the cell channel layerfilling the third openings by removing the second conductive layerfilling the second openings; and forming the junction layer by forming athird conductive layer filling the second openings.
 18. The method ofclaim 17, wherein the second conductive layer and the third conductivelayer comprise polysilicon layers doped with respective impuritieshaving opposite conductive types.
 19. The method of claim 13, wherein,in the forming of the third openings, the second insulation layer isremoved to remain as a shape of a pillar.
 20. The method of claim 19,wherein, in the forming of the cell channel layer, the cell channellayer is filled in the third openings and fanned as a shape of a planepenetrated by the pillar.